Mitsubishi Spindle Encoder MBE90K

The MBE90K is a high-resolution spindle encoder assembly used in CNC machine tools (especially with Mitsubishi AC spindle/servo systems) for C-axis control, spindle speed feedback, and orientation detection. It is typically mounted on the spindle end to provide precise position and speed information back to the CNC controller.

🔧 Basic Construction

• The MBE90K unit comprises two gears, two sensors, and a pre-amplifier module.

  • One sensor/gear pair provides C-axis position feedback.

  • The other sensor/gear pair provides speed (rotation) feedback.

• Each set (e.g., MBE90K-01A, -02A, etc.) includes specific gear and sensor combinations optimized for particular spindle configurations.

🌀 Function & Role in CNC

• C-axis Control: Provides very accurate angular position information of the spindle for C-axis machining (contouring around the spindle axis).

• Orientation & Rigid Tap: The encoder allows the controller to know the exact angular orientation of the spindle, essential for rigid tapping, spindle indexing, and synchronized machining operations.

• Speed Feedback: The speed signal helps the drive precisely regulate spindle RPM and improve servo performance.

• This high resolution makes fine spindle control and high-accuracy motion possible.

📊 Typical Signals & Outputs

• The MBE90K sensors produce multi-phase signals (e.g., X, Y, C, D phases) used for positioning and speed calculation.

• These signals are typically conditioned by the pre-amplifier before being sent to the CNC/spindle drive system for processing. The exact waveform characteristics (e.g., sine waves, pulse widths) are adjusted during installation to meet the controller’s spec.

🧰 Installation & Adjustment Notes

• Proper gap and phase adjustments between sensors and gears are important for accurate signal generation.

• Adjustments are usually made via small potentiometers on the pre-amp board using an oscilloscope.

• Installation instructions in Mitsubishi documents emphasize correct gear/sensor matching and waveform setup to ensure reliable speed and orientation signals.

📍 Typical Applications

• Spindle feedback on CNC milling and turning centers

• C-axis precision machining

• Rigid tapping and synchronized spindle motion

• High-accuracy positioning control loops

• Works with Mitsubishi CNC and spindle drive systems (e.g., MDS-C1, MDS-SP, FR-SF series).